buenas he visto lo que tienes puesto y he ententado hacer lo que tu dices haciendo el minimo cambio espero que te sirva aqui te dejo la hoja de estilo css y el html
<html><head>
<link rel="STYLESHEET" type="text/css" href="estilos.css">
</head>
<body>
<div class="post-content">
<p>Parrafo 1</p>
<p>Parrafo 2 - Parrafo 2 - Parrafo 2</p>
<p>Parrafo 3 - Parrafo 3 - Parrafo 3 - Parrafo 3 </p>
<div class="uno" >
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
</div>
<div class="dos" >
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
</div>
<div class="dos" >
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
<p><a rel="lightbox" href="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1.jpg"><img class="alignleft size-thumbnail wp-image-86" title="ananashahotel_1" src="
http://www.enmancora.com/wp-content/uploads/2010/12/ananashahotel_1-150x150.jpg" alt="" width="150" height="150" /></a></p>
</div>
</div>
</body></html>
hoja de estilo
p {
padding: 0px 0px 0px 0px;
margin:0px;
}
img {text-align:center;
margin-top:50px;
}
.uno {text-align:center;
width:33%;
height:33%;
float:right;
}
.dos {width:33%;
height:33%;
float:left;
text-align:center;
}
espero que te haya podido ayudar
suerte.